I assume you've noticed that this is a bit of a mess. Certain pins on the MicroSquirt Module (uSM) can be wired directly to the mating pins on the 4-channel Driver (4D). Others need a few interposing components.

Connect uSM IGN1 and IGN2 (one wire each) to 4D Ignition 1 & 2.Connect uSM WLED and ALED to 4D Ignition 3 & 4. Remove the R330 base resistor on the 4D for these circuits; replace with a jumper link. Use the R330 resistor as a pull-up resistor to 5V (uSM VRef).

Delete 4D Q5 and Q6, as well as the associated resistors. Connect uSM INJ1 and INJ2 (two pins each; 5 is overkill) directly to the large pads of Q5 and Q6.Connect uSM PT6 and PT7 to 4D Injector 3 & 4.

Ok thank you very much, yes I saw that it was more complicated than expected. Fortunately you are here to help me and I thank you. Electronics this is not my field. Well I 'm trying to do this without losing myself and without bullshit . Jeremy

However, I would use 1K resistors instead of 330R because that's what I use with the IGBTs provided in my kits. If you use BIP373s purchased somewhere else then use 330R pull ups. You can use the unused R3 and R4 resistors for this purposes.

The ground on the DB15 needs to be connected to the car ground and is for the high current ground for the injectors and coils; the ground on the input side needs to be connected to the MS board and is the logical ground. If the DB15 is not connected, the high current ground is not connected and there is only a connection through the injector and coil drivers so a high resistance is normal.

If the DB15 is connected to the board with the other end connected to the car ground and the MS is also connected to the car as it should for normal operation, you should see a reading of 0 Ohm between the two grounds.